The present invention relates to devices and methods for treating dilatation of the valves at the base of the heart by external stabilization of the base of the heart, which subtend the atrio-ventricular valves of the heart.
Dilatation of the base of the heart occurs with various diseases of the heart and often is a causative mechanism of heart failure. In some instances, depending on the cause, the dilatation may be localized to one portion of the base of the heart (e.g., mitral insufficiency as a consequence of a heart attack affecting the inferior and basal wall of the left ventricle of the heart), thereby affecting the valve in that region. In other cases, such as cardiomyopathy, the condition may be global affecting more of the heart and its base, causing leakage of particularly the mitral and tricuspid valves. Other conditions exist where the mitral valve structure is abnormal, predisposing to leakage and progressive dilatation of the valve annulus (area of valve attachment to the heart). This reduces the amount of blood being pumped out by the ventricles of the heart, thereby impairing cardiac function further.
In patients with heart failure and severe mitral insufficiency, good results have been achieved by aggressively repairing mitral and/or tricuspid valves directly, which requires open-heart surgery (Bolling, et al). The mitral valve annulus is reinforced internally by a variety of prosthetic rings (Duran Ring, Medtronic Inc) or bands (Cosgrove-Edwards Annuloplasty Band, Edwards Lifesciences Inc). The present paradigm of mitral valve reconstruction is therefore repair from inside the heart, with the annulus being buttressed or reinforced by the implantation of a prosthetic band or ring. Since this is major open-heart surgery with intra-cavitary reconstruction, there is the attendant risk of complications and death associated with mitral valve surgery. Another approach has been to replace the mitral valve, which while addressing the problem, also requires open-heart surgery and involves implantation of a bulky artificial, prosthetic valve with all its consequences. Because every decision to perform major surgery requires some risk vs. benefit consideration, patients get referred for risky surgery only when they are significantly symptomatic or their mitral valve is leaking severely.
In contrast to the more invasive approaches discussed above, in specific instances of inferior left ventricular wall scarring causing mitral regurgitation, Liel-Cohen and co-workers have suggested localized pressure or support of the bulging scar of the inferior wall of the heart from the outside (Liel-Cohen. N. et al. (2000) xe2x80x9cDesign of a new surgical approach for ventricular remodeling to relieve ischemic mitral regurgitation: insights from 3-dimentsional echocardiographyxe2x80x9d. Circulation 101 (23):2756-2763).
Another less invasive approach to preventing global heart dilation is ventricular containment with a custom made polyester mesh, or cardiac support device (U.S. Pat. Nos. 6,077,218 and 6,123,662). These devices are designed to provide a passive constraint around both ventricles of the heart, and constrain diastolic expansion of the heart. Other devices include ventricular assist devices that provide cardiac assistance during systole and dynamic ventricular reduction devices that actively reduce the size of the heart. However, this technique does not specifically address valve leakage using a device that reinforces the base of the heart in all phases of the cardiac cycle.
Accordingly, there is a need to provide a less invasive, simple technique of repairing, reinforcing, reducing or stabilizing the base of the heart and its underlying valves (mitral and tricuspid valves) from the outside.
The present invention addresses the problems discussed above by providing a device for the treatment of certain heart disorders, in particular mitral and/or tricuspid valve insufficiency. The device aims to reduce the size of the base of the heart that contains these valvular structures. In addition, the present invention can be used to address progressive dilatation of any localized area of the heart, such as the atrial or ventricular myocardium, or the cardiac base. It does so by providing external re-enforcement or remodeling of the cardiac base. As used herein, the surgical procedure for implanting the device is referred to as ibasal annuloplasty of the cardia externally (xe2x80x9cBACExe2x80x9d) and the device is referred to as the external cardiac basal annuloplasty system (xe2x80x9cECBASxe2x80x9d) or BASE System.
In one embodiment, a customized or specially constructed biocompatible strip is implanted along the base of the heart at the level of the atrio-ventricular groove. The strip or mesh is between 2 and 5 cms wide and is secured by 2 rows of clips or sutures, one on the atrial side and the other on the ventricular side of the atrio-ventricular groove. Specific care is taken to avoid injury to the circumflex and right coronary arteries and the coronary sinus. This procedure may be performed either as a stand-alone procedure or as an adjunct to other cardiac surgery. Additionally, it may be performed with or without the aid of cardio-pulmonary bypass.
Another embodiment of this approach is a device or strip, which once implanted at a certain size, can be tightened over time either by inflation of an attached chamber or programmed to return to a pre-formed size (based on elasticity or pre-existing memory) of the material used.
Another embodiment of this device, while externally stabilizing the base of the heart, also provides a localized increase in contraction along any segment of the base to improve contractile function. This may be accomplished by the aid of contractile metal or modified muscle or other cells.
Variations of the device include a complete stabilization of the base of the heart, or a partial stabilization around the expansile portions of the mitral and tricuspid valves by a biocompatible strip.
Another variation seeks to use ports along the device that will facilitate delivery of specialized drugs, gene therapeutic agents, growth factors, etc.
A specific variation incorporates the use of epicardial bi-ventricular pacing electrodes implanted along with the BACE-Sys, where multi-site pacing might be indicated.
The invention also provides a method of implantation, which may be through a conventional full median sternotomy with the strip being secured by sutures, or a minimally invasive approach whereby the device/strip may be implanted by a specialized implantation system using adhesives, self-firing clips, sutures, etc.
Another modification of this technique is the local application of prosthetic material to stabilize scars of the heart to prevent their expansion (local ventricular stabilization).
In an alternate embodiment, the device incorporates additional strips to be used in concert or as an extension to provide localized support to areas of ventricular reconstruction or areas of fresh infarction or old scar.